This invention relates to inkjet ink imaging, particularly to inkjet ink image recording elements and to a method for their production.
In a typical inkjet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of carrier liquid, in particular a solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol or a polyhydric alcohol or a mixed solvent of water and one or more water-miscible solvents such as a monohydric alcohol or a polyhydric alcohol.
The recording elements typically comprise a support or a support material having on at least one surface thereof an ink-receiving or image-forming layer. The elements include those intended for reflection viewing, which usually have an opaque support, and those intended for viewing by transmitted light, which usually have a transparent support.
Although a wide variety of different types of image-recording elements for use with inkjet ink devices have been proposed heretofore, there are many unsolved problems in the art and many deficiencies in the known products which have severely limited their commercial usefulness. The requirements for an image-recording medium or element for ink-jet recording are very demanding.
It is well known that in order to achieve and maintain photographic-quality images on such an image-recording element, the recording element should
Be readily wetted so there is no puddling, i.e. coalescence of adjacent ink dots, which leads to nonuniform density.
Exhibit no image bleeding.
Exhibit the ability to absorb high concentrations of ink and dry quickly to avoid elements blocking together when stacked against subsequent prints or other surfaces.
Provide a high level of gloss and be sufficiently insoluble in typical ink solvents to avoid the development of differential gloss.
Exhibit no discontinuities or defects that are due to interactions between the support and/or layer(s), such as cracking, repellencies, comb lines and the like.
Not allow unabsorbed dyes to aggregate at the free surface causing dye crystallisation, which results in bloom or bronzing effects in the imaged areas.
Be optimised for image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light.
Image recording elements for inkjet ink images (also referred to herein as inkjet media or inkjet receivers) conventionally have a top or xe2x80x9covercoatxe2x80x9d layer coated on top of the ink-receiving or imaging-forming layer, the latter also referred to herein as a base layer. An overcoat layer has been used, in particular, when the base layer contains gelatin or a polymer. The overcoat layer can server various functions, such as to provide physical protection for the underlying layer, reduce tackiness, provide a glossy appearance, offer an ink-receptive surface, carry specific components or allow easier manufacture. The overcoat layers are usually thinner than the underlying base layer typically used for inkjet receivers, such an overcoat layer being commonly about 1 micron (xcexcm) thick.
As noted above, it is desirable that the inkjet medium or receiver should dry quickly after the application of the ink. It has been found that by omitting the top or overcoat layer it is sometimes possible to reduce the time taken to dry a printed image (as measured by the density of ink transferred to a piece of plain paper sandwiched to the printed image immediately after it exits the inkjet printer). However, this is an unsatisfactory way of improving the drying time, for it entails the loss of the advantageous properties that the overcoat layer was intended to provide.
The present invention, in one of its aspects, provides an image recording element for ink images, especially inkjet ink images, comprising, in the following order, a support, an ink-receptive layer and a top layer, wherein the top layer comprises a polymer that contains both a hydrophilic component and a hydrophobic component, or a mixture of two or more such polymers, the said polymer or polymer mixture being present in the top layer in an amount of from 0.003 to 0.5 g/m2, and wherein the top layer has been hardened with an oxazoline functional polymer.
The present invention, in another aspect thereof, also provides a method for the preparation of an image recording element for ink images, especially inkjet ink images, which method comprises the steps of forming a precursor element comprising a support and an ink-receptive layer and forming a top layer on the surface of the precursor element remote from the support by applying to the said surface a polymer that contains both a hydrophilic component and a hydrophobic component, or a mixture of two or more such polymers, the polymer or polymer mixture being applied at a rate of from 0.003 to 0.5 g/m2 and in conjunction with an oxazoline functional polymer.
The ink-receptive layer is also referred to herein, for convenience, as a xe2x80x9cbase layerxe2x80x9d. However, the presence of one or more additional layers, for example on the side of the support remote from the base and top layers or situated between the support and the said base layer or situated between the base layer and the top layer, is not precluded.